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NORA Oilheat Technicians Manual

Chapter 13 Heating Systems Chapter 13 Heating Systems Chapter 13—Heating Systems 13-3 This chapter introduces the basic principles of oil-fired heating systems. Part I Warm air furnaces Furnaces create warm air that is distributed through the building through ducts. A warm air furnace utilizes a metal heat exchanger that is designed to absorb heat from the oilburner flame and transfer that heat to the air that circulates through the furnace and into the house. It accomplishes this by having the burner fire into a combustion chamber which is adjacent to the heat exchanger. The resulting combustion gases are vented to a chimney via the flue pipe. This heated air is then distributed to the house through supply ducts while cold air from the building is brought back to the furnace through return ducts, see Figure 13-1 The advantage of warm air systems is air cleaners, humidifiers, and central air conditioning systems can be incorporated into the unit to provide a total comfort indoor air quality climate control system. Warm air furnaces have a blower attached to their ducts. The airflow the blower creates is measured in CFM (Cubic Feet Per Minute). It is important that the blower and ducts be properly sized to move enough air across the heat exchanger to remove the heat from the furnace and deliver it to the house. The normal operation of a warm air furnace is as follows: 1. Thermostat calls for heat and activates the burner through the primary control. 2. Burner runs until a sufficient amount of heat is built up to activate the fan control and start the blower. (Usually 140 degrees) 3. The burner and blower run together until the thermostat has been satisfied and the burner shuts off. Figure 13-1: Typical warm air furnace Heat Exchanger Fan Limit Control Combustion Chamber Primary Combustion Control Filter Return Air


NORA Oilheat Technicians Manual
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